In recent years, the amount of data (information) used in executing businesses or the like at enterprises and used in services required for the social life have been increasing. Accordingly, a storage device which is capable of storing such large amount of data and of utilizing the stored data at right time is demanded, for example, at server rooms, data centers and the like.
As an example of such a storage device which includes a plurality of portable cartridges (recording media) is known, wherein each of them contains a recording medium such as a magnetic tape (for details of such library device, refer to Japanese Patent Publication No. 3630408).
In the library device, a recording medium specified by a command which is received from another external device such as a server device (referred to a “server device” as a representative example in the following description) is conveyed to a drive device by the use of a conveyance mechanism. The drive device writes data into the conveyed recording medium or reads data from the recording medium, and thereby exchanges those pieces of data with the server device.
For example, the library device can be shared by a plurality of server devices.
When sharing the library device, such a plurality of server devices communicate with each other using a communication network (hereafter, referred to also as simply a “network”) in order to avoid a situation where accesses compete with each other (hereafter, the situation is referred to also as simply “access contention”).
As a result, communication traffic between the plurality of server devices increases, and processing load of each server device increases in association with it. Additionally, if one of the server devices is forced to wait as a result of the above-described avoidance of access contention between the server devices, availability of the server is lowered.
In order to deal with such a situation, in a library device shared by a plurality of server devices, a plurality of recording media included in the library device are generally divided into some groups of which includes a predetermined number of medium storage slot so that the process for avoiding access contention does not need to be performed between the server devices. Accordingly, a plurality of physical libraries is created.
In the library device, the logical libraries are correlated on a one-to-one basis with the above-described physical libraries each of which included of the predetermined number of medium storage slot, and the plurality of server devices are correlated on a one-to-one basis with the logical libraries.
Because the library devices have the above-described configuration, it becomes possible to make the situation that each of the server devices have an own library device and can exclusively use the own library device.
Japanese Patent Application Laid-Open No. 2005-122843 discloses a technology of dividing physical libraries included in a library device into a plurality of logical libraries and performing data which is transferred between server devices which are correlated on a one-to-one basis with the plurality of logical libraries which is created by the division.
Specifically, a library device, which is described in Japanese Patent Application Laid-Open No. 2005-122843 notifies, in its inside, insertion of a recording medium to a host which is the destination of data transfer, and makes the host which is the destination of data transfer recognize the inserted recording medium. In this way, Japanese Patent Application Laid-Open No. 2005-122843 discloses a technology for transferring data between hosts in a shorter time than for transferring the data by once ejecting a recording medium outside and inserting it again.
Japanese Patent Application Laid-Open No. 2011-095812 discloses a technology of performing a process described below when a logical volume recorded in a primary storage means (a disk array device) is copied to a recording medium for secondary storage (a tape library device). The process is that, when a target logical volume is a volume which is ejected outside on the basis of ejection identification information, the volume which is ejected outside is copied to a recording medium for external ejection in parallel with the process of copying the logical volume to a recording medium for secondary storage.
Specifically, there is a problem that, when an ejection request is received from a host, it takes a long time since the reception until all logical volumes designated are copied to a recording medium for secondary storage and ejection of the recording medium for secondary storage after the copying becomes possible. With regard to the problem, Japanese Patent Application Laid-Open No. 2011-095812 discloses a technology which can perform the ejection in a short time by creating a recording medium for external ejection in parallel with copying to a recording medium for secondary storage.
However, the library device mentioned above has a problem described below.
In the library device mentioned above, a recording medium is required for recording new data into it. It is also required to backup data recorded in a recording medium or to store data in a recording medium for a long period of time. Because of these sorts of necessity, operations of inserting the recording medium into the library device from outside and of extracting (ejecting) it from the library device are performed. These operations are usually performed, for example, at a closure of a business or the like, and hence are not frequently performed.
Therefore, in the library device, for example, the number of physical slots from which a recording medium is ejected (ejection slot) is not so large as the number of server devices using the library device (that is, the number of logical libraries created by the division and correlated with the server devices as described above). Accordingly, the physical ejection slots are shared by a plurality of server devices.
Here, the ejection slots are referred to as physical slots within the library device which are used, for example, by an operator to extract a recording medium into which the library device has recorded data, via an extraction opening from which a recording medium can be extracted, in order to eject the recording medium outside the library device for the purpose of, for example, long-term storage of the recording medium at another place. The ejection slots may be able to contain a plurality of recording media.
An application program executed at a server device so as to control the library device issues an instruction (ejection request) to cause the library device to eject a recording medium desired to be ejected, among recording media which are stored in the physical slot constituting a physical library correlated with a logical library related to the server device, to the ejection slots. Here, there may be a case a plurality of server devices each issue such an ejection request simultaneously with the others.
When ejection requests are issued simultaneously from a plurality of applications, as mentioned above, and the shared ejection slots can contain a plurality of recording media, for example, recording media ejected in accordance with the respective ejection requests, each from among recording media which are stored in the physical slot constituting a physical library correlated with a logical library related to the corresponding server device. Therefore, the recording media are mingled with each other at the ejection slots.
Accordingly, there arises a problem in that an operator needs to sort the ejected recording media to identify which logical library is correlated with, and it takes a lot of trouble.
In the library device having the shared ejection slots, until completion of extracting a recording medium from a logical ejection slot assigned to a logical library, no other logical libraries accept a request for ejecting a recording medium. Accordingly, there arises a problem in that server devices controlling the other logical libraries are forced to suspend issuing a request for ejecting a recording medium.
Japanese Patent Application Laid-Open No. 2005-122843 mentioned above gives no consideration for ejecting a recording medium to the outside of the library device. Therefore, the disclosure of Japanese Patent Application Laid-Open No. 2005-122843 is limited to a technology of, in transferring data by correlating a tape recording medium with a different logical library within a library device having a plurality of logical libraries created by the division described above, determining a logical library whose related tape recording medium is not ejected to be a target logical library to which the data is to be transferred.
In the technology disclosed in Japanese Patent Application Laid-Open No. 2011-095812 mentioned above, for example, a plurality of hard disk drives included in a disk array device being a primary storage means are divided into groups each consisting of a predetermined number of hard disk drives, and each of the groups of hard disk drives is correlated with a logical library. However, Japanese Patent Application Laid-Open No. 2011-095812 discloses nothing about correlating the logical libraries, already correlated with the hard disk drive groups, on a one-to-one basis with a plurality of server devices.